LIKE DI­A­MONDS IN THE SKY

(Ref. to the song Di­a­monds by Ri­hanna, 2012)

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In

the mar­ket­places of planet Earth di­a­monds are both de­sir­able and scarce, and that makes them ex­pen­sive. Both the de­mand and the rar­ity are, how­ever, largely ar­ti­fi­cial. Di­a­monds were made de­sir­able in the 20th cen­tury mainly by a marketing campaign from De Beers, a big South African pro­ducer of the stones. The scarcity was, un­til re­cently, a re­sult of the same com­pany—which at one point con­trolled about 90% of the world’s pro­duc­tion— en­sur­ing that the num­ber of stones which found their way into the world’s jewellery shops was well reg­u­lated.

2. In na­ture, though, di­a­monds are un­re­mark­able. They are sim­ply crys­tals of car­bon, al­beit crys­tals of a type that needs a fair amount of pres­sure to form. And car­bon is the fourth-most abun­dant el­e­ment in the uni­verse. For that rea­son, as demon­strated in a pa­per just pub­lished in Na­ture As­tron­omy, they are prob­a­bly avail­able in em­bar­rass­ing abun­dance in the cos­mos.

COS­MIC JACK­POT

3. Do­minik Kraus, a physi­cist at the Helmholtz Cen­tre in Dres­den, and his col­leagues, are in­ter­ested in ice-gi­ant plan­ets, such as Uranus and Nep­tune. Ice gi­ants are rich in heavy el­e­ments such as oxy­gen, ni­tro­gen and, cru­cially, car­bon. That car­bon is locked up in com­pounds, mostly hy­dro­car­bons such as meth­ane and eth­ane.

4. Ice gi­ants, as the name sug­gests, are also big. This means that, in the depths of their thick at­mos­pheres, tem­per­a­tures are high enough to split those hy­dro­car­bons into hy­dro­gen and car­bon, and pres­sures are suf­fi­cient to com­press the car­bon into di­a­monds. The con­se­quence, 10,000km or so be­neath the top of the at­mos­phere, is a con­stant rain of di­a­monds.

5. This re­search will be of in­ter­est to more than gem-cut­ters of the dis­tant fu­ture look­ing for new sources of sup­ply. Know­ing the tem­per­a­ture and pres­sure at which parts of an ice gi­ant’s at­mos­phere start to de­com­pose into their ele­men­tary con­stituents can help as­tronomers fix the re­la­tion­ship be­tween the ra­dius and mass of such plan­ets. Know­ing how they re­late will help cat­a­logue just how many more di­a­mond-en­crusted plan­ets are lurk­ing out there in the cos­mos.

Di­a­monds are prob­a­bly avail­able in em­barass­ing abun­dance in the cos­mos.

It is rain­ing di­a­monds. Lit­er­ally. As demon­strated by sci­en­tists when recre­at­ing the at­mo­spheric con­di­tions of Uranus and Saturn. Us­ing poly­styrene and a laser, they have man­aged to con­firm the hy­poth­e­sis for­mu­lated by re­searchers long ago: it rains pre­cious stones on these plan­ets.

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